Youth bullying is a critical public health problem with 20-28% of American middle school youths victimized annually. Targeted youths often experience a wide-range of significant psychosocial, academic, and physical problems; moreover, being bullied as a youth contributes to poorer life outcomes throughout adulthood. A reduction in the prevalence of youth bullying is an objective of Healthy People 2020 and the focus of significant state and federal legislation. The majority of interventions designed to identify and reduce bullying are school-based. Unfortunately, substantial research has demonstrated only modest improvements in bullying activity that have been difficult to sustain. Victimized youths are reluctant to seek help from school staff and school administrators have limited jurisdiction when bullying occurs off of school property. Therefore, there is a critical ned for healthcare providers to begin taking an active, systematic role in screening for youth bullying as they do for other common youth health concerns. Healthcare professionals are limited currently in their ability to effectively screen patients for bullying exposure as there are no brif screening measures for bullying appropriate for busy healthcare settings. Yet, over 90% of middle school youths have at least one visit to a healthcare provider annually, often for concerns where bullying is a factor. Without a valid and reliable tool such as those used in screening for other common health problems, these youth healthcare encounters represent millions of missed opportunities for the early identification and intervention with those exposed to bullying. This lag in identification and subsequent intervention for those affected is critical n that it allows time for negative health squeal to develop. Therefore, the goal of this study is to develop a psychometrically robust youth screening tool -the CABS: Child-Adolescent Bullying Screen--appropriate for widespread use in healthcare environments. To achieve this goal, a mixed methodological approach will be used including: 1) initial instrument development using focus groups and follow-up surveys with key informants, 2) instrument testing using classical test theory and Rasch analysis, and 3) evaluation of the CABS' diagnostic performance through assessment of its sensitivity, specificity, positive and negative predictive values, accuracy, and the area under the receiver operating characteristic curve.